System and method for detecting an acoustic signal in the presence of flow noise

Abstract

A system and method are provided for detecting an acoustic signal in the presence of flow noise produced by the turbulent flow field that develops about a hosewall of a towed array. Pressure is sensed with pressure sensors at two diametrically-opposed locations at the surface of the hosewall over a period of time. The sensed pressure signals are used to generate an ensemble-averaged cross-spectra which effectively cancels out the flow noise while retaining the acoustic signal associated with a possible target of interest.

1. A system for detecting an acoustic signal in the presence of flow noise produced by the turbulent flow field that develops about a hosewall of a towed array being towed through the water, said system comprising:
 sensing means for sensing pressure at two diametrically-opposed locations at the surface of the hosewall over a period of time; and 
 processing means coupled to said sensing means for generating an ensemble-averaged cross-spectra using said pressure so-sensed over the period of time. 
 
   
   
     2. A system as in  claim 1  wherein said sensing means comprises a pair of pressure sensors potted in the hosewall with each of said pair being located at one of said two diametrically-opposed locations. 
   
   
     3. A system as in  claim 2  wherein said pressure sensors comprise ceramic pressure sensors. 
   
   
     4. A system as in  claim 1  wherein said processing means comprises:
 means for digitizing said pressure so-sensed over the period of time at each of said two diametrically-opposed locations, wherein a corresponding pair of digitized sequences of pressure measurements are generated; 
 means for performing a Fast Fourier Transform (FFT) on each of said pair of digitized sequences wherein a corresponding pair of FFTs are generated; and 
 means for generating said ensemble-averaged cross-spectra using said corresponding pair of FFTs. 
 
   
   
     5. A system for detecting an acoustic signal in the presence of flow noise produced by the turbulent flow field that develops about a hosewall of a towed array being towed through the water, said system comprising:
 a first pressure sensor mounted in the hosewall for measuring pressure fluctuations at a surface of the hosewall at a first location thereon; 
 a second pressure sensor mounted in the hosewall for measuring pressure fluctuations at the surface of the hosewall at a second location thereon, said first and second locations being diametrically-opposed to one another; and 
 a processor coupled to said first and second pressure sensors for generating an ensemble-averaged cross-spectra using said pressure fluctuations at said first and second locations. 
 
   
   
     6. A system as in  claim 5  wherein said first and second pressure sensors comprises ceramic pressure sensors. 
   
   
     7. A method of detecting an acoustic signal in the presence of flow noise produced by the turbulent flow field that develops about a hosewall of a towed array being towed through the water, said method comprising the steps of:
 sensing pressure at two diametrically-opposed locations at the surface of the hosewall over a period of time; and 
 generating an ensemble-averaged cross-spectra using said pressure so-sensed over the period of time. 
 
   
   
     8. A method according to  claim 7  wherein the towed array includes (i) a plurality of sensing elements located along a central axis of the towed array, and (ii) a telemetry system coupled to said sensing elements for transmitting measurements made by said sensing elements to an end user thereof, wherein said step of generating includes the step of using characteristics of the telemetry system in generating said ensemble-averaged cross-spectra. 
   
   
     9. A method according to  claim 8  wherein said characteristics include the frequency range and sampling rate of the telemetry system.